<template>
  <div class="spec-preview">
    <img :src="images.imgUrl" />
    <!-- 遮罩板底下的大图 -->
    <div class="event" @mousemove="changeMove"></div>
    <!-- 右侧大图 -->
    <div class="big">
      <img :src="images.imgUrl" ref="big"/>
    </div>
    <!-- 遮罩层 -->
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    props:['imageList'],
    computed:{
      images(){
        return this.imageList[this.currentIndex]||{};
      }
    },
     data(){
      return {
        currentIndex:0
      }
  },
    methods:{
      changeMove(event){
            let big = this.$refs.big
            let mask = this.$refs.mask
          let l = event.offsetX-mask.offsetWidth/2
          let t = event.offsetY - mask.offsetHeight/2
          if(l<=0){
            l = 0
          }
          if(l>=mask.offsetWidth){
            l = mask.offsetWidth
          }
          if(t <= 0){
            t = 0
          }
          if(t>=mask.offsetHeight){
            t = mask.offsetHeight
          }
          mask.style.left = l +'px'
          mask.style.top = t +'px'
          big.style.left = -2*l +'px'
          big.style.top = -2*t +'px'
      }
    },
    mounted(){
      this.$bus.$on('send',(index)=>{
          this.currentIndex = index
      })
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>